<!DOCTYPE html
  PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN"
  "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">
<html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en" lang="en">
<head>
<style>
table { border-collapse: separate; border-spacing: 5px; margin: 1px; border: 1px solid black; }
td { border: 1px solid grey; width: 10px; height: 10px; padding: 2px;}
td td { border: 1px solid green; }
td td td { border: 1px solid red; }
</style>
</head>
<body>

<table>
<tr>
<td>
  <table>
  <tr>
  <td>foo</td>
  </tr>
  <tr>
  <td>bar</td>
  </tr>
  </table>
</td>
</tr>
</table>

<table style="margin-top: 1em; width: 300px;">
<tr>
<td>
  <table>
  <tr>
  <td>
    <table>
    <tr>
    <td colspan="2">a</td>
    </tr>
    <tr>
    <td>b</td>
    <td>c</td>
    </tr>
    </table>
  </td>
  <td rowspan="2">d</td>
  </tr>
  <tr>
  <td>e</td>
  </tr>
  </table>
</td> 
<td>f</td>
</tr>
<tr>
<td>g</td>
<td>h</td>
</tr>
</table>    

</body>
</html>